She writes that between early February and late April she completed three months of surgical procedures to remove both breasts.

During that time, Jolie, a former United Nations goodwill ambassador, continued her humanitarian work around the globe – including a visit to the Republic of Congo and the G8 Summit in London.

Jolie, 37, writes that she made the choice with thoughts of her six children after watching her own mother, actress Marcheline Bertrand, die too young from cancer at the age of 56 at 2007.

“My mother fought cancer for almost a decade and died at 56,” Jolie writes. “She held out long enough to meet the first of her grandchildren and to hold them in her arms. But my other children will never have the chance to know her and experience how loving and gracious she was.”

She writes that, “They have asked if the same could happen to me.”

Jolie said that after genetic testing she learned she carries the “faulty” BRCA1 gene and had an 87 percent chance of getting the disease herself.

“Once I knew that this was my reality, I decided to be proactive and to minimize the risk as much I could,” she writes. “I made a decision to have a preventive double mastectomy.”

Dr. Elisa Port, director of the Dubin Breast Center at Mount Sinai Medical Center, said the gene is very rare.

“It’s always helpful to hear what’s going on with others and to raise awareness, but clearly this does not apply to most women in the general population,” Port told CBS 2’s Weijia Jiang.

But as CBS 2’s Jessica Schneider reported, the operation greatly reduces the likelihood that Jolie will contract cancer.

“Once someone has the prophylactic surgery, the risk of developing breast cancer is probably in the order of 5- to maybe up to 10 percent, but probably closer to 5 percent,” said Dr. Stephanie Bernik of Lenox Hill Hospital.

WATCH: Q&A With Dr. Gomez

Jolie said she has kept the process private so far, but wrote about it with hopes of helping other women.

“I wanted to write this to tell other women that the decision to have a mastectomy was not easy. But it is one I am very happy that I made,” Jolie writes. “My chances of developing breast cancer have dropped from 87 percent to under 5 percent. I can tell my children that they don’t need to fear they will lose me to breast cancer.”

She is anything but private in the details she provides, giving a description of the procedures.

“My own process began on Feb. 2 with a procedure known as a ‘nipple delay,”’ she writes, “which rules out disease in the breast ducts behind the nipple and draws extra blood flow to the area.”

She then describes the major surgery two weeks later where breast tissue was removed, saying it felt “like a scene out of a science-fiction film,” then writes that nine weeks later she had a third surgery to “reconstruct the breasts and receive implants.”

Jolie said she has nothing to hide from her six children, and they do not need to fear losing her to breast cancer.

“They can see my small scars and that’s it,” she wrote. “Everything else is just Mommy, the same as she always was.”

Many women have chosen preventative mastectomy since genetic screening for breast cancer was developed, but the move and public announcement is unprecedented from a star so young and widely known as Jolie.

She briefly addresses the effects of the surgery on the idealized sexuality and iconic womanhood that have fueled her fame.

“I do not feel any less of a woman,” Jolie writes. “I feel empowered that I made a strong choice that in no way diminishes my femininity.”

She also wrote that Brad Pitt, her partner of eight years, was at the Pink Lotus Breast Center in Southern California for “every minute of the surgeries.”

“We managed to find moments to laugh together,” she writes. “We knew this was the right thing to do for our family and that it would bring us closer. And it has.”

Pitt hailed Jolie’s decision as “heroic” and told the London Evening Standard Tuesday “This is a happy day for our family.”

“Having witnessed this decision firsthand, I find Angie’s choice, as well as so many others like her, absolutely heroic,” he said. “All I want for is for her to have a long and healthy life with myself and our children.”

Jude Callirgos, a stage four breast cancer fighter and author of “Breast Left Unsaid,” told 1010 WINS that she believes Jolie’s decision can help a lot of women who are thinking about having the procedure.

“I was very proud of her to come out and to talk about it so openly,” Callirgos said. “It’s something that a lot of women go through and have to make that very, very difficult decision and sometimes receive a lot of negative judgment about it.”

“It’s a terrible decision to have to make, but Angelina Jolie, just with her ability to be able to come out and associate her name and her experience with this disease, I think is going to be tremendously helpful to a lot of women and also men,” Callirgos added.

Bertrand, Jolie’s mother, died in January 2007. She had small roles in the movies “Lookin’ to Get Out” in 1982 and “The Man Who Loved Women” in 1983. She raised Jolie and her brother after divorcing their father, Oscar-winning actor Jon Voight, when Jolie was a toddler.

Jolie has been vocal about her mother’s battle with cancer and spoke about her in 2011 on “60 Minutes.”

“I will never be as good a mother as she was,” she said. “I will try my best, but I don’t think I could ever be. She was grace incarnate, the most generous, loving — she’s better than me.”

Jolie has appeared in dozens of films including 2010’s “The Tourist” and “Salt,” the “Tomb Raider” films, and 1999’s “Girl, Interrupted,” for which she won an Academy Award.

But she has appeared more often in the news in recent years for her power coupling with Pitt and her charitable work with refugees as a United Nations ambassador.